1. Field of the Invention
The present invention relates to a novel phenylalanine derivative, more particularly to a phenylalanine derivative having a proteinase inhibition activity or a pharmaceutically acceptable salt thereof. The present invention also relates to a proteinase inhibitor containing the phenylalanine derivative as the effective ingredient.
2. Description of the Related Art
It is well known in the art that various proteinases are present in human organisms. Examples of such proteinases are plasmin, trypsin, kallikrein, urokinase, and the like. As is also known, when these proteinases are abnormally activated for some reason, various diseases are caused. For example, hemorrhagic diseases are caused when abnormally activated plasmin is present in a relatively large amount in the blood. Also, plasmin participates in inflammation and it is considered to cause inflammatory diseases. For this reason, a substance capable of exhibiting a proteinase inhibition activity is useful as a clinical remedy or medicine, and various investigations in the prior art have been made for the development of such substances. For example, antiplasmins are useful as hematostatic agents, antiinflammatory agents or antiallergic agents, antitrypsins are useful for the therapy of pancreatitis, antikallikreins are useful as therapeutical agents for inflammation, and antiurokinases are useful for the inhibition of hemorrhagic symptoms in the thrombolytic therapeutical method with urokinase. Accordingly, developments of proteinase inhibitors having such activities have progressed in the prior art, but their proteinase inhibition activities are low and not satisfactory for practical application as medicines. Further, compounds having satisfactory inhibition activities against various proteinases have not been developed.